Northwesterly winds have been causing hot temperatures for eastern parts of New Zealand at the start of 2019, and MetService says the hot temperatures are expected to continue into the weekend.

The northwesterly winds are strongest about the Tararua District and Wairarapa north of Masterton, where a Severe Weather Watch is in place until 11pm tonight.

'When we get these northwesterly winds across New Zealand's mountain ranges, a phenomenon called the Foehn Effect causes all the moisture in the air to condense into cloud or rain on the western side of the mountains keeping areas in the west cloudy,” explains MetService Meteorologist Claire Flynn.

'The air is dried out as it moves over the mountains, and then heats up on the journey down the leeward side, meaning hot weather in the east.”

Today, temperatures in the east of the North Island and upper South Island are set to hit or exceed 30C.

However, a cold front moving northwards up the South Island on Thursday and over the North Island on Friday will cause temperatures to drop back just a few degrees in the east, but it will still be warm.

'The weak front will reach the upper South Island late on Thursday. Eastern parts of the North Island will likely see temperatures in the thirties again today, but the weak cold front will cool things off a fraction as it makes its way further north on Friday. The front will not bring much in the way of rain, however.”

Northwesterly winds are set to return this weekend, with temperatures in eastern parts of both islands reaching the thirties once more. Gisborne is expected to be the warmest spot, with 33C forecast for Sunday.

It is good news for some of New Zealand's largest sporting events on over the weekend too, with fine weather forecast in Tauranga for the cricket and in Auckland for the tennis.

The northwesterly winds precede yet another cold front, though this time a more significant one – bringing rainfall to the west of the South Island from Saturday, and to the southeast of the South Island on Sunday.

Meanwhile, further afield, MetService has been watching some action in the Pacific.

The Bureau of Meteorology in Australia have renamed Tropical Cyclone Penny, while further east, Tropical Cyclone Mona is situated north of Fiji. MetService have been keeping a close eye on this system as it develops, and more details can be found at http://bit.ly/TropicalCycloneActivity